Polluted Rivers Can Turn Into Airborne Hazards, New Study Warns

A new study published in Science Advances (May 28, 2025) reveals a disturbing environmental link: polluted river water can become aerosolised upon entering the ocean, releasing harmful compounds into the air that humans can inhale. This discovery significantly expands the known risks of river pollution, particularly in urban-industrial regions like parts of India.

Background

• Historically, human settlements grew around rivers for agriculture, water, and sanitation.
• Today, however, many rivers, especially in developing countries, have become channels for untreated sewage and industrial effluents, harming ecosystems and public health.

Study Location and Methodology

• Conducted by scientists in California on the Tijuana River, which flows from Mexico into the Pacific Ocean.
• Timeframe: January to March 2020
• Methods:
  • Daily seawater sampling and 24-hour air filtration using quartz-fibre filters at five locations along 35 km of coast.
  • Special focus during rain events, which intensify pollution flow.

Contaminants Monitored

• 12 common wastewater-related human-made compounds were tracked using high-resolution liquid chromatography–mass spectrometry.
• Substances included:
  • Octinoxate (sunscreen ingredient)
  • Dibenzylamine (tire rubber additive)
  • Methamphetamine, illicit drugs
  • Benzoylecgonine (cocaine metabolite used as sewage proxy)
  • Prescription drugs and agricultural biocides

Key Findings

• 10 out of 12 compounds were more concentrated in river-influenced seawater.
• Aerosols from river-adjacent sites had the highest pollution loads.
• Strong correlations found between benzoylecgonine and levels of methamphetamine, octinoxate, and dibenzylamine, suggesting a common source: untreated wastewater.
• Estimated air emissions per 1 km of coastline:
  • 1 kg of octinoxate
  • 100 g of methamphetamine
  • Several grams of tire additives

Global Implications

• Globally, such coastal pollution could aerosolise and release approximately:
  • 40,000 tonnes of octinoxate
  • 50 tonnes of dibenzylamine into the air each year.
• Chronic inhalation risks remain unquantified, especially for fisherfolk and marginalised communities living near polluted coasts.

India-Specific Relevance

• Many rivers in India, such as the Yamuna, Ganga, and Mithi, are heavily polluted and flow into seas, raising concerns about similar airborne toxic exposure in densely populated coastal zones like Mumbai, Chennai, and Kolkata.
• Environmental justice concerns emerge as the poor bear disproportionate health burdens from both water and now air pollution.

TH